Lighting and daylighting in livestock buildings for dairy cows - Circadian lighting and energy use

Abstract

The industrial sector of Sweden used 136 TWh of energy 2022 out of which the agricultural sector used 6.09 TWh. The goal of the country is to become 50% more energy efficient by 2030 compared to 2005. Furthermore, Sweden’s long-term target is to achieve net zero greenhouse gas emissions by 2045. From 2005-2022 the total energy use of the agricultural sector has been reduced by 16% but previous studies have shown that there is a great savings potential in the replacement of electric lighting or an increase in the utilization of daylight. A switch to newer electric lighting technology is imminent as on a European level the Ecodesign and the Restriction of Hazardous Substances (RoHS) directives have called for a phase out of T5, T8 and compact fluorescent light sources starting in 2023. These fluorescent light sources contain toxic mercury and are less energy efficient compared with LED. The replacement is calculated to save at least 42 TWh within the EU. As of 2023, the total Swedish bovine cattle population was approximately 1.5 million. These animals spend large parts of the year indoors; however, the buildings do not always provide optimal conditions in terms of daylighting and electric lighting. The reasons to consider a good lighting environment can be the cost of replacing old lighting fixtures, fire safety, the practicality of changing old non-LED light sources, energy use and cost as well as animal and worker welfare. The goal of this thesis is to suggest a good lighting environment for cows and human caretakers while achieving low energy use, which supports sustainability and low cost of food.
Switching from fluorescent to LED results in new lighting intensities and spectrums, impacting the circadian conditions indoors. Milk production rate is greatly impacted, with an average increase of 2.5 kg/cow per day by allowing responsive span of lighting availability in a day and the Swedish Board of Agriculture states that lighting and daylighting should support circadian and behavioural needs in cattle. This paper contains the results of simulations where more energy-efficient electric lighting was implemented while utilizing and improving daylighting potential in livestock buildings. The buildings studied were located at Rosdala Gård (55°34’ N, 14°17 E), in the east of Skåne, Sweden. Three cattle buildings were studied; they are connected to a milking facility through a passageway. The newest, middle, and oldest buildings have areas of 3337 m², 2683 m², and 2037 m², respectively. Physical and photometric measurements were performed on site. Daylight and lighting measurements were conducted using a photometer and illuminance meter on an overcast day. The 3D modelling was performed using Rhinoceros according to site measurements. Climate Studio and ALFA from Solemma were used for daylighting, electric lighting, and circadian lighting simulations. Using measured material reflectance’s as input for simulations, the resulting daylight factors are compared to those obtained through site measurements. Finally, improvements are suggested and implemented in the model and these simulation results are compared with the base case results.
In the study we show that both the replacement of fluorescent light sources with LED light sources and utilizing of daylight harvesting proved to have a high energy saving potential. The electric lighting improvements resulted in a reduction of 48 and 63% in the middle and old building respectively. The daylight harvesting potential and the circadian lighting conditions inside the old building could be greatly improved with the implementation of a skylight, increasing the daylight autonomy from 12 to 55%. Other measures, such as increasing the reflectance of interior surfaces, did not prove effective at increasing the daylighting potential. The daylighting savings potential observed on the buildings in this study were 50 to 60%. In the circadian studies it was found that the daylight provided vastly more illuminance compared with the electric lighting and the buildings with skylights showed a high melanopic illuminance during daytime.

Popular Abstract

Curious about livestock facilities for cows in a Nordic country? Excellent! Countries all over the world pursue efforts to reduce their energy demands. But what about the cows? In agricultural buildings housing dairy cows, there is a large potential to reduce the energy demand for electric lighting. Efficient electric lighting and daylighting through daylight harvesting systems have great potential to lower the energy use. The varying impact of light on different species is a fascinating example of nature’s evolutionary design. Lighting can be designed to increase milk production in dairy cows while being energy efficient. The lighting plays a crucial role not only from an energy point of view, but also for the circadian conditions inside the buildings. The lighting affects the circadian clock through special retinal cells in the eyes, regulating the sleep-wake cycle through the release of the hormone melatonin. The interesting physiological changes cows undergo under the influence of light, found in assorted literatures, forms the basis of this study on energy use and lighting conditions in agricultural buildings. Switching from fluorescent lights to LEDs has the potential to reduce energy use for lighting by 48 to 63%. Daylight harvesting can also contribute to energy savings, with reductions of up to 57%. This is done through sensors adjusting lights according to daylight levels by either turning them on and off or by dimming them. Fenestration is crucial in these building. Natural light through windows, and most importantly skylights, not only saves energy, but also outperforms electric lighting in regulating circadian rhythms.
This work is an investigation of three livestock buildings for cattle, with a total area of 8057 m2, constructed between 1990 to 2014 at Rosdala Gård in southern Sweden. Information from on-site measurements was utilized to assess daylighting, electric lighting, and circadian lighting conditions through various simulation software. Improvements on building design and electric lighting were investigated, aiming to reduce energy use and improve lighting conditions. Both cows and human caretakers will benefit from the improved designs, which impacts both the fenestration and electric lighting.
The benefits of reducing current energy use lie not only in achieving environmental goals but also in reducing electricity costs for the dairy industry. The number of dairy cows in Sweden is not insignificant, amounting to nearly 300,000 cows, while the total number of cattle is 1.5 million. As a reference the capital, Stockholm, has a population of approximately 1 million humans. Providing good conditions for the cows is important not only to maintain high quantity and quality of milk but also to ensure the social sustainability of the industry.
This study can be used to estimate the impact of replacing fluorescent lighting with LED lighting, as well as the effectiveness of similar buildings in utilizing daylight harvesting. The study results provide insight into how lighting affects the circadian conditions inside the buildings and the importance of daylight for these conditions. The literature review provides information on how cows are affected by the lighting conditions.
While light studies with humans often encompass both health and productivity, studies involving cows focus primarily on productivity, either in terms of milk yield or quality. Additionally, these studies use metrics aimed at describing human visual perception of light. Not only does this not capture the cow’s perception, even when studying humans this does not describe the full effect of the light. The non-visual effects of light are controlled by different photoreceptors in the eye, sensitive to different wavelengths.
In our study it was found to be important to pay special attention to achieving even light distribution. If the light is too uneven, cows may move slower or even refuse to move at all, as their visual acuity is poorer than that of humans. They cannot distinguish between a shadow or a hole in the ground. Both the placement of the light fixtures and the angle at which the fixtures spread the light are important to consider. In our study, the fixtures selected had too narrow distribution angle, leading to poor uniformity and failing to meet the requirements.
It was surprising to find that cows and humans are not so different from each other when it comes to circadian responses. Only a 6 to 12% difference in melanopsin irradiance was found for the electric light sources. Peak sensitivities are at very similar wavelengths, and the melatonin suppression thresholds occur at similar light levels. The study of the non-visual effects of light based on species-specific sensitivities is a novel and fascinating field of research in agricultural science. With the opportunity of more precise, comparable, and optimised results, the future looks bright for the cows.

• author: Nordin, Karl Axel and Zaw, Phoo Wint
• supervisor: Marie-Claude Dubois; Sheikh Rishad Ahmmad
• organization: Department of Building and Environmental Technology; Division of Energy and Building Design
• course: AEBM01 20241
• year: 2024
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: Energy efficiency, dairy cows, circadian lighting, daylighting
• language: English
• id: 9162469
• date added to LUP: 2024-06-13 13:07:58
• date last changed: 2024-06-13 13:07:58